When configuring a Linux computer running Sendmail
you must/can do the following things
You must minimally specify the intended purpose of your computer, mail wise: Is it a workstation or the mail server ? What is the domain used for email ? ...
You can setup exception in the routing. If you know a short cut to a specific site or domain, you can tell Sendmail here. This is especially needed to connect uucp sites to the Internet.
Some users may want to receive their email under different
name, or you want to set a "pseudo" user and direct
the mail of this user to a real user. A good example
is postmaster
.